- vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 42028] IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43911 SUBJECT: IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility DATE: 26/03/03 18:33:37 GMT FROM: Jannis Necker at DESY <jannis.necker(a)desy.de> Jannis Necker (Leiden University), Akshay Eranhalodi (DESY), Robert Stein (JSI), and Anna Franckowiak (Ruhr University Bochum) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-260217A (Zegarelli et. al, GCN 43768) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2026-02-22 02:51 UTC, approximately 116.9 hours after event time due to bad weather. We covered 100.0% (0.7 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 30s with a typical depth of 20.5 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019) . No candidate counterparts were detected. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; OKC, Sweden; DZA, Germany. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/43911. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42027] GRB 260228A: SVOM/ECLAIRs refined analysis
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43910 SUBJECT: GRB 260228A: SVOM/ECLAIRs refined analysis DATE: 26/03/03 15:29:58 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. G. Bernardini (INAF-OAB, LUPM), M. Brunet, J.-L. Atteia, O. Godet (IRAP), W. J. Xie (NAOC), Y. Julakanti, R. A. J. Eyles-Ferries (Leicester Univ.) report on behalf of the SVOM/ECLAIRs team: Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 260228A (SVOM burst-id 26022802). The burst that triggered ECLAIRs onboard (GCN 43882) consists of a double-peaked pulse with a duration of T90 = (18.3 -4.0/+16.0) s in the 4-120 keV energy band. Since the GRB is observed mainly below 20 keV, we also computed the duration in the 4-20 keV energy band: T90 = (22.9 -4.2/+9.4) s. The time-averaged spectrum from T0+7 s to T0+31 s (T0 = 2026-02-28T20:55:34.620) in the energy range 5-120 keV is best fitted by a broken power-law model with alpha_1 = (-1.33 -0.43/+0.34), alpha_2 = (-2.83 -0.33/+0.37) and E_break = (9.6 -0.9/+1.2) keV. With this model, the total 4-120 keV fluence is (4.27 -2.6/+0.2)E-7 erg/cm^2. All the quoted errors are at the 68% confidence level. With these parameters, the Eiso ranges from 1.6E49 erg assuming z=0.1 to 8.6E52 erg at z=10. The location of GRB 260228A in the Amati plane for different redshifts is available here: https://drive.google.com/file/d/1FfPqOo6kSt6L5QR-DGjUvxdrTwvSlPfT/view?usp=… The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Maria Grazia Bernardini (INAF-OAB, LUPM) (maria.bernardini at inaf.it) View this GCN Circular online at https://gcn.nasa.gov/circulars/43910. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42026] GRB 260225A: SVOM/ECLAIRs refined analysis
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43909 SUBJECT: GRB 260225A: SVOM/ECLAIRs refined analysis DATE: 26/03/03 14:56:16 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, O. Godet (IRAP), W.J. Xie (NAOC), F. Daigne (IAP),Yinuo Ma (NAOC), Li Zhang (IHEP) report on behalf of the SVOM/ECLAIRs team Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260225A (SVOM burst-id sb26022501 – GCN 43829, trigger time T0 = 2026-02-25T08:51:15 UTC). The burst that triggered ECLAIRs shows a single peak lightcurve. The burst duration before the satellite slew is estimated through imaging to be around 59 s (from T0-21 s up to T0+209 s) in the 4-120 keV energy band. Some emission below 20 keV is still seen after the slew up to T0+209 s. The time-averaged spectrum before the satellite slew, i.e. from T0-21 s to T0+38 s in the 5-120 keV energy band is best fitted by a broken power-law model with a first photon index of -1.00 +0.20/-0.16, a break energy of 21.7 +4.4/-3.9 keV and a second photon index of -2.06 +0.22/-0.28. With this model, the 4-120 keV fluence is (1.00 +0.04/-0.26)e-6 erg/cm^2. The spectral parameters indicate that this burst is likely to be an X-ray flash. All the quoted errors are at the 68% confidence level. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/43909. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42025] GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43908 SUBJECT: GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559) DATE: 26/03/03 14:05:07 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 794237065 at 13:24:20 on 03 March 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 13.0 deg Decl.(2000.0) = -27.8 deg The 1 sigma statistical error radius is 1.3 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260303559/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260303559/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260303559/json View this GCN Circular online at https://gcn.nasa.gov/circulars/43908. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42024] GRB 260303B: Fermi GBM Final Real-time Localization
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43907 SUBJECT: GRB 260303B: Fermi GBM Final Real-time Localization DATE: 26/03/03 13:34:53 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 13:24:20 UT on 3 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260303B (trigger 794237065.456588 / 260303559). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 9.3, Dec = -26.7 (J2000 degrees, equivalent to J2000 00h 37m, -26d 41'), with a statistical uncertainty of 1.6 degrees. The angle from the Fermi LAT boresight is 67.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260303559/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260303559/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260303559/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43907. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42023] EP260302a: analysis of the follow-up EP-FXT observation
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43906 SUBJECT: EP260302a: analysis of the follow-up EP-FXT observation DATE: 26/03/03 11:54:52 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. J. Zhang (THU), Y. H. Cheng, D. Zhu, K. J. Zhang (YNU), H. W. Pan (NAOC) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260302a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission at 2026-03-02T23:52:58 (UTC) (Zhang et al., GCN 43899), and was followed by several telescopes (Li et al., GCN 43898, Pérez-García et al., GCN 43903, Corcoran et al., GCN 43904). The X-ray source detected by WXT exhibited a flare within the first 100 seconds of the observation. The X-ray source detected by WXT has a 0.5--4 keV flux of approximately 1.4 x 10^-10 erg s^-1 cm^-2, with an power-law index of 1.1. The NH value is fixed to galactic value (8.6 x 10^20 cm^-2). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically, starting at 2026-03-02T23:54:17(UTC), about 2 minutes after the trigger. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 132.9717 deg, Dec. = -65.9839 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The uncatalogued X-ray source revealed a decline in its light curve during the FXT observation. Its X-ray spectrum has a 0.5–10 keV flux of 1.84(+0.05/-0.04) x 10^-10 erg s^-1 cm^-2, with a power-law index of 1.46(+0.04/-0.04) and a NH value of 8.6 x 10^20 (fixed galactic value) + 5.7 (+1.5/-1.4) x 10^20 cm^-2. All errors are performed with 90% significance. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43906. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42022] EP260227a: Gemini-South optical observations
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43905 SUBJECT: EP260227a: Gemini-South optical observations DATE: 26/03/03 10:58:44 GMT FROM: Laura Cotter at University College Dublin <laura.cotter(a)ucdconnect.ie> R. A. J. Eyles-Ferris (Leicester), J. Quirola-Vasquez (Radboud), G. Corcoran (UCD), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), , A. J. Levan (Radboud), D. B. Malesani (DAWN/NBI and Radboud) report on behalf of a larger collaboration: We observed the optical counterpart of the fast X-ray transient EP260227a (Wang et al., GCN 43869) with the Gemini-South telescope equipped with the GMOS-S instrument, obtained 12x60 s exposures in the r band starting at 2026-03-03 05:52:34 UT (t_mid = 81.9 hr). In our stacked image, we detect a faint source coincident with the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al, GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris and Tanvir et al., GCN 43875; Malesani et al., GCN 43876; Eyles-Ferris et al., GCN 43877; Strausbaugh et al., GCN 43879; Bochenek et al., GCN 43880; Gassert et al., GCN 43881; Gupta et al., GCN 43884; Ma et al., GCN 43887; Eyles-Ferris et al., GCN 43888; Zhong et al., GCN 43891; Volnova et al., GCN 43894). In our preliminary photometry, we measure an AB magnitude of r = 24.80 +/- 0.33 calibrated to Pan-STARRS and not corrected for Galactic extinction. It is unclear at this stage whether this is continued transient emission or the underlying host galaxy. View this GCN Circular online at https://gcn.nasa.gov/circulars/43905. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42021] EP260302a: LCO observations
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43904 SUBJECT: EP260302a: LCO observations DATE: 26/03/03 10:57:45 GMT FROM: Laura Cotter at University College Dublin <laura.cotter(a)ucdconnect.ie> G. Corcoran (UCD), L. Cotter (UCD), J. Chacón (PUC), J. A. Quirola-Vasquez (Radboud), A. Martin-Carrillo (UCD), F. E. Bauer (UTa), P. G. Jonker (Radboud) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260302a (Zhang et al., GCN 43899) with the LCO 1m telescope located at the Cerro Tololo Inter-American Observatory (Chile) equipped with the SINISTRO instrument. We obtained 6 x 300 exposures in each of the r and z filters, starting on 2026-03-03 at 02:20:48 UT (~2.46 hr post the EP trigger). In our stacked images for both filters we detect the optical counterpart reported by Li et al. (GCN 43898) and Perez-Garcia et al. (GCN 43903), with the following magnitudes: r = 20.84+/-0.11 z = 20.38+/-0.14 The counterpart has faded significantly since the previous reports. These values are in the AB system and are calibrated to Pan-STARRS. These values are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43904. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42020] EP260302a: BOOTES-7 optical counterpart detection at early times
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43903 SUBJECT: EP260302a: BOOTES-7 optical counterpart detection at early times DATE: 26/03/03 08:37:18 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Pérez-García, S.-Y. Wu, E. Fernandez-García, M. D. Caballero-García, M. Gritsevich, R. Sánchez-Ramírez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Pérez del Pulgar (Univ. de Málaga), Y.-D. Hu (GXU), D. R. Xiong (Yunnan Observatories of CAS), B.-B. Zhang (Nanjing Univ.) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report: Following the detection of the fast X-ray transient EP260302a by the Einstein Probe (Zhang et al. GCN 42899), the 0.6m BOOTES-7 robotic telescope at San Pedro de Atacama (Chile) observed the fast X-ray transient location starting on Mar 3, 00:04:05 UT (11.1 min after trigger) in different optical bands. On a coadd of clear-filter images (4x60s, 00:10:26 UT, mid exposure time) we detect at early times the optical counterpart reported by LCO 1 hr after the trigger (Li et al. GCN 43898), within the EP/FXT 20 arcsec radius error circle, with 19.1 +/- 0.2 mag. We thank the staff at San Pedro de Atacama Celestial Explorations observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43903. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42019] GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
by GCN Circulars 03 Mar '26

03 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43902 SUBJECT: GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate DATE: 26/03/03 07:31:10 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> Benjamin Schneider (LAM), Rosa L. Becerra (UNAM), Jean-Grégoire Ducoin (CPPM), Jean-Luc Atteia (IRAP), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Antonio de Ugarte Postigo (LAM), Ziqi Wang (GXU) and Defeng Kong (GXU) report: We imaged the field of the SVOM GRB 260303A (Wang et al., GCN Circ. 43901) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-03-03 06:02:58 to 06:24:06 UTC (from 81 seconds after the trigger or 30 seconds after the notice until to 24 minutes after the trigger) and obtained 700 seconds of simultaneous exposure in the r and z filters. The data were reduced, coadded, calibrated, and analyzed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect an uncatalogued source just outside the ECLAIRs error circle (Wang et al., GCN Circ. 43901) at: RA(J2000) = 06:12:45.06 = 93.1877 degrees Dec(J2000) = +41:09:04.4 = 41.1512 degrees with an uncertainty of 0.5 arcsec. The preliminary magnitudes derived for that source are: r = 18.69 +/- 0.01 z = 18.19 +/- 0.02 The source is observed to rise and then fall in both r and z. Further observations are ongoing. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0